Compression resistant zinc base alloy with high wear resistance

ABSTRACT

ZINC BASE ALLOY CONSISTING BY WEIGHT OF ABOUT 2 TO ABOUT 15% ALUMINUM, ABOUT 2 TO ABOUT 10% COPPER, ABOUT 0.01 TO ABOUT 0.15% MAGNESIUM, ABOUT 0.02 TO ABOUT 0.15% BERYLLIUM, ABOUT 0.01 TO ABOUT 0.05% TITANIUM, ABOUT 0.01 TO ABOUT 3% SILVER AND THE BALANCE OF ZINC, HAS SUPERIOR WEAR RESISTANCE AND SUPERIOR COMPRESSION RESISTANCE EXTENDING TO ABOUT 80 TO ABOUT 70 KG./MM.2 OF COMPRESSIVE STRENGTH AND ABOUT 32 TO ABOUT 43 KG./MM.2 OF PROOF STRESS ON COMPRESSIVE DEFORMATION AT ABOUT O.2% OFFSET.

March 13, 1973 TAKEHRO 5055 ET AL 3,720,510

COMPRESSION RESISTANT ZINC BASE ALLOY WITH HIGH WEAR RESISTANCE Filed July 22. 1971 3 1400 3 Q3 E \J /200 3 t, g g 1000- Q 2- k 80 Q Q E 600 3 ,0 g Q g I b 400 M \Q Q.

3 00 at L JD 7O no /20 Load on bra/mg. (Kg/c07 United States Patent O 3,720,510 COMPRESSION RESISTANT ZINC BASE ALLOY WITH HIGH WEAR RESISTANCE Takelliro Isobe, Yama, Toshio Shimazu, Tokyo, and Koji Ogawa, Yukio Arake, Aizu Wakamatsu, and Tatsuji Hashimoto, Yama, Japan, assiguors to Nisso Smelting Co., Ltd., Tokyo, Japan Filed July 22, 1971, Ser. No. 165,016 Claims priority, applicatsiggzJijlpan, July 27, 1970,

US. Cl. 75-178 AM 2 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates to an improvement in zinc base alloys, and more particularly concerns a compression and wear resistant zinc base alloy having superior resistance properties, such as wear resistance of about 80 to about 170 kg./mm. of compressive strength and about 32 to about 43 kg./mm. of proof stress oncompressive deformation.

BRIEF DESCRIPTION OF THE PRIOR ART Heretofore, a zinc base alloy has been proposed named Zamak 2 containing 3.5 to 4% of aluminium, 3.5 to 4% of copper, 0.03 to 0.06% of magnesium as a compression resistant, and zinc base alloy for good performance as forming die.

However, previous zinc base alloys including Zamak 2 have not proved entirely satisfactory because they have less than about 65 kg./mm. of compressive strength and 23 kg./mm. of proof stress on compressive deformation at best.

In US. patent application Ser. No. 724,376 filed Apr. 26, 1968, now Pat. 3,567,436 dated Mar. 2, 1971, one of the present inventors and his co-inventor describe a zinc base alloy containing by weight 2 to 15% aluminium, 2 to copper, 0.01 to 0.15% magnesium, 0.02 to 0.15 beryllium and 0.01 to 0.5% titanium as alloy constituents which has superior compression resistance and more preferably, a zinc base alloy containing by weight, 2.5 to 7% aluminium, 3 to 7% copper, 0.04 to 0.10% magnesium, 0.04 to 0.10% beryllium and 0.08 to 0.15% titanium which has superior compression resistance with high compressive strain on fracture, and is suitable for casting. However, this zinc base alloy does not have an altogether satisfactory wear resistance.

SUMMARY OF THE INVENTION It has now been discovered, in accordance with the present invention, that when a small amount of about 0.01 to about 3.0% silver is added into the aforesaid alloy, wear resistance is markedly improved andthe alloy containing silver is very suitable for use as a bearing. More than 0.01% of silver accelerates the intermetallic compound and improves the bearing property of the alloys and the intermetallic compound can, be easily observed by micro- 3,720,510 Patented Mar. 13, 1973 scope. More than 3% of silver does not contribute further to the acceleration of the bearing property. Namely, a zinc base alloy consisting by Weight of about 2 to about 15% aluminium, about 2 to about 10% copper, about 0.01 to about 0.15% magnesium, about 0.02 to about 0.15% beryllium, about 0.01 to about 0.05% titanium, about 0.01 to about 3% silver and the balance zinc, more preferably containing about 2.5 to about 7% aluminium, about 3 to about 7% copper, about 0.04 to about 0.10% magnesium, about 0.04 to about 0.10% beryllium, about 0.08 to about 0.15% titanium, about 0.01 to about 3.0% silver and the balance zinc, has Wear resistance properties With good seizing quality, high heat conductivity, and high electric conductivity, in addition to hardness, tensile strength, compressive strength, and compressive strain.

OBJECTS OF THE INVENTION Accordingly it is an object of this invention to provide a zinc base alloy having high wear resistance, high compressive strength and high proof stress on compressive deformation.

It is another object to provide a zinc base alloy having high compressive strength with high compressive strain on fracture.

It is yet another object to provide a zinc base alloy having high compressive strength with superior bearing properties.

It is also another object to provide a zinc base alloy having enough high fluidity and castability to be used for a gravity casting process offering a beautiful casting surface.

It is a further object to provide a zinc base alloy preventing intermetallic corrosion.

This invention Will further become apparent from the following description and accompanying drawing:

The sole drawing figure is a graph described in the examples.

DETAILED DESCRIPTION Each limitation of the other elements is based on the following reasons. Addition of beryllium to the alloy improves compression resistance and about 0.02% or more of beryllium prevents intermetallic corrosion not accompanied by deterioration of castability, however, beryllium over about 0.15% makes it difiicult to alloy and moreover the alloys become expensive. Titanium also improves the compression resistance in co-operation With beryllium, however, addition of titanium over about 0.5 causes a TiZn intermetallic compound and the addition of less than about 0.01% titanium does not cause a Zn-Cu-Ti intermetallic compound. Addition of aluminium in a range of about 2% to about 15% gives the most desirable compression resistance.

Furthermore, from a viewpoint of compression resistance, the added amount of copper is specified in a range of about 2 to about 10% contrariwise, the addition of copper over about 10% has a bad influence on the metallographic structure, for example, the grain size of the structure becomes rough and another phase sometimes occurs. About 0.01% or a higher amount of magnesium acts to prevent intermetallic corrosion, however, if over about 0.15 thereof is added, the brittleness of the alloy is increased. In giving the foregoing percentages, the term about is used since these percentages are somewhat interdependent, and may be varied by a very, very slight amount by compensation or toleration of an undesired condition.

If the amounts of each alloy constituent are not kept Within the aforesaid limitations, wear resistance, proof stress on compressive deformation markedly decreases and compression resistance deteriorates or other properties are affected, for example, fluidity is decreased or brittleness is increased.

3 In addition to wear resistance, compression resistance, proof stress and high compressive strain which is a barometer of nonbrittleness and toughness, the zinc base alloy of this invention has the following properties:

(1) The melting point varies from about 375 to about 4 Lower test piece: carbon steel Hv 230 40 mm. x 10 mm. Revolution of lower test piece: 185 r.p.m. Load: 40 kg. Lubricant: Mineral oil #120 dropping method, 0.4 cc./

min.

. 430 C., in conformity with the aluminium and copper Friction distance: 25 km. content percentages. Room temp.: 20 C.

The i i 1S shghtly deteriorated m conformlty Amounts of wear were measured by means of balancing with the aluminium or copper content percentage, howthe used test plates. ever, the zinc base alloy has a sufficiently high fluidity to produce cast products having complicated forms and Results r llsted In Table 2- beautiful casting surfaces by die-casting or gravity casting. TABLE 2 (3) Usual zinc base alloys containing aluminium tend i to suffer an intermetallic corrosion caused by the impuri- Thls mventlon ties included therein, such as lead, tin, cadmium and in- Alloy Amount of dium; however, in the alloy of this invention, intermetallic Wear corrosion is prevented by the addition of magnesium and/ 1 or beryllium. For example, after steam treatment for 240 2 hours at 95i5 'C., a tolerance of more than 0.15% d 3 not occur. After artificial aging for 40 days at 65 C., a 4 tolerance does not occur further. 5 (4) Plating may be carried out as easily as the plating 6 for a common zinc base alloy. 7 (5) The specific gravity of this alloy is 6.6 to 7.3. 8 The zinc base alloy of this invention has numerous ad- 9 vantages, especially, superior wear resistance, 80 to 170 10 l g./mm. of superior compression resistance of compres- 11 sive strength and 32 to 43 kg./mm. of proof stress on 12 compression deformation and suitability for die-casting 13 and gravity casting sufiicient to gain a beautiful casting 14 surface and high compressive strain of fracture. 15

The zinc base alloy has many uses such as forming macomparison terial, piston material, pressure instrument parts, spring All Amount f boxes, machine parts, bearings, type and bushings for N w (mg) back and fore, power shovel, wheel accelerator and con- 16 18.4

veyer. 17 16.5 For the purpose of giving those skilled in the art a 1g 14 3 better understanding of the invention, as well as a better 19 15.2 appreciation of the advantage of the invention, the follow- 20 155 ing examples of the invention are given by way of illus- 21 29.0 tration. 22 24.1 Some examples of alloy containing silver in this in- 23 14.0 vention are listed in Table 1. Tin-bronze 17.0

TABLE 1 Alloy constituents, percent Alloy N0. Al Cu Mg Be Ti Ag Zn Note Tliisinvention(containingAg) 2.0 3.0 0.04 0.04 0.1 0.5 Balance-.." 4.0 3.0 0.04 0.04 0.1 0.5 .do. 6.0 3.0 0.04 0.04 0.1 05.-...(10.-. 4 10.0 3.0 0.04 0.04 0.1 0. 2.0 7.0 0.1 0.1 0.3 0. 4.0 7.0 0.1 0.1 0.3 0. 6.0 7.0 0.04 0.1 0.3 0. 0.0 7.0 0.1 0.1 0.3 0. 9.0 8.0 0.04 0.15 0.15 0. 0 3.5 0.05 0.04 0.00 0. .0 2.0 0.04 0.04 0.1 0. .5 3.5 0.04 0.04 0.1 0.0 .5 3.5 0.04 0.04 0.1 0.0 .5 3.5 0.04 0.04 0.1 1. .5 3.5 0.04 0.04 0.1 3.

Comparison .0 3.0 0.04 do .0 3.0 0.04 0.04 .0 3.0 0.04 .1 do. .0 3.5 0.04 0.04 0.1 do .0 3.5 0. 04 d .0 o. 04 .0 1.0 0. 04 .0 3.0 0. 04

EXAMPLE 1 Testing machine: Amsler wear testing machine Test piece: 10 mm. width x 37 mm. length x 3 mm. thickness EXAMPLE 2 Seizing quality of alloys were tested. Various pipes of alloys, having a 52 mm. diameter x 30 mm. diameter x 95 mm. length, were casted by centrifugal casting and 2- 0 divided bearings being 50 mm. in diameter x 40 mm. diameter x 32 mm. wide were cut off from the pipes by machining and further polished.

The divided bearings were set in a bearing box and used as sleeve bearings supporting a tempered carbon steel shaft being 40 mm. in diameter. Load was charged on 

